Mangroves are critical fish and invertebrate habitats, however, identifying to what degree species are affiliated to mangrove systems remains challenging. Here we outline and apply two quantitative and one qualitative method for assessing the degree of mangrove affiliation globally at a species level, based on habitat-specific fish and invertebrate species densities extracted from an exhaustive search of the literature, for mangroves and their associated coastal habitats. We assessed all 121 species for which we had ≥7 mangrove records and where data allowed, quantified the percentage contribution of mangroves to the summed species density across all habitats. We set the threshold for identifying a species as "highly mangrove-affiliated" as ≥70% relative density, and examined its validity by subjecting a subset of species either side of the threshold to a thorough review of evidence for mangrove affiliation in the peer reviewed literature. We found that 53 were highly mangrove-affiliated, including 24 fish and three invertebrate species from the Atlantic East Pacific, and nine fish and 15 invertebrate species from the Indo West Pacific (n = 2 had global distributions). 36 of the 53 species are of value to artisanal, subsistence or commercial fisheries; 21 in the Atlantic East Pacific, and 13 in the Indo West Pacific. While this list of highly mangrove-affiliated species is far from complete due to data limitations, it represents the first attempt to undertake a global overview of highly mangrove-affiliated species, and a proof of concept for a quantitative and objective method of assessment.